The present invention relates to a method for determining an acoustic response attributed to a location of an impact, like a touch event on a surface of an object, and a touch sensing device implementing the method.
Methods to determine the location of an impact on a surface of an object based on analysing acoustic signals are already known in the art. This kind of technology is based on measuring the acoustic signal using one or more sensors to obtain an acoustic signature of the impact and to compare the signature with a predetermined set of acoustic signatures, wherein each predetermined acoustic signature is representative for a given location of the haptic or tactile interface. The location of the impact is then identified based on the similarity of its acoustic signature with one of the predetermined acoustic signatures. FIG. 1 schematically illustrates such a prior art device with an interaction surface 101 and two transducers 103.
It has also been observed, that the predetermined set of acoustic signatures generated by computing the individual acoustic pattern of closely spaced locations 105 on the surface of a haptic interface during the calibration of the device as illustrated in FIG. 1 and described above, can be falsified due to some spurious noise contributions to the sensed signals during the calibration phase. To obtain a desired precision unwanted noise sources need to be identified and the experimental set-up adapted accordingly. This represents a tedious and time consuming activity and in addition it is not always possible to identify all unwanted contributions.
It is therefore the object of the invention to provide a method for reducing noise contributions to sensed acoustic signals.